1. Field of the Invention
The present invention relates to a surface light source and a light guide plate used in the surface light source, and particularly to a surface light source and a light guide plate having a color filter.
2. Prior Art
In general, liquid crystal displays (LCDs) have two main advantages in comparison with cathode ray tubes (CRTs): LCDs are thin, and have low power consumption. It has been said that LCDs might one day completely replace CRT display devices, and LCDs have aroused great interest in many industries in recent times. In general, an LCD needs a surface light source to provide even light for a clear display.
FIG. 5 shows a conventional LCD 100, which comprises a liquid crystal panel 101 and a back light source 102 emitting light beams into the liquid crystal panel 101. The liquid crystal panel 101 has a first substrate 2, a Thin Film Transistor (TFT) substrate 7, and a liquid crystal layer 5 installed between the first substrate 2 and the TFT substrate 7. An top polarizer 1 and a bottom polarizer 8 are mounted on outsides of the first substrate 2 and the TFT substrate 7, respectively. A color filter 3 and a transparent electrode layer 4 are stacked on an inside of the first substrate 2 in that order from top to bottom. The transparent electrode layer 4 is made from Indium Tin Oxide (ITO). A TFT electrode 6 is disposed on the TFT substrate 7. The back light system 102 comprises a prism plate 9, a diffuser 10, a light guide plate 11, and a light source 12 emitting light beams into the light guide plate 11. The prism plate 9 and the diffuser 10 are stacked on the light guide plate 11 from top to bottom in that order. The light guide plate 11 changes directions of the incoming light beams, and transmits the light beams into the liquid crystal panel 101.
FIG. 6 shows the color filter 3 disposed on the first substrate 2. The color filter 3 comprises: a black matrix 14 formed on the first substrate 2 in a lattice pattern using a method such as photolithography; a color layer 13 filling and covering spaces defined in the black matrix 22 with color materials such as dyes, organic pigments or inorganic pigments, the color layer 13 being formed using photolithography; and a resin film layer 15 covering the color layer 13 and the black matrix 14. In the LCD 100, the color filter 3 is always disposed on the first substrate 2 of the LCD panel 101, and is an important element for realizing a high quality color display. However, the process for manufacturing the color filter 3 on the first substrate 2 is complex. Therefore, the cost of the first substrate 2 is correspondingly high.
A new light guide plate providing the function of color filtering is desired to overcome the above-described problems.